rp2/machine_i2c: Use pico-sdk's default pins for I2C.

Inherits the default values for whichever instance is PICO_DEFAULT_I2C.
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

ports/rp2/machine_i2c.c

@@ -35,14 +35,24 @@
 #define DEFAULT_I2C_FREQ (400000)
 
 #ifndef MICROPY_HW_I2C0_SCL
+#if PICO_DEFAULT_I2C == 0
+#define MICROPY_HW_I2C0_SCL (PICO_DEFAULT_I2C_SCL_PIN)
+#define MICROPY_HW_I2C0_SDA (PICO_DEFAULT_I2C_SDA_PIN)
+#else
 #define MICROPY_HW_I2C0_SCL (9)
 #define MICROPY_HW_I2C0_SDA (8)
 #endif
+#endif
 
 #ifndef MICROPY_HW_I2C1_SCL
+#if PICO_DEFAULT_I2C == 1
+#define MICROPY_HW_I2C1_SCL (PICO_DEFAULT_I2C_SCL_PIN)
+#define MICROPY_HW_I2C1_SDA (PICO_DEFAULT_I2C_SDA_PIN)
+#else
 #define MICROPY_HW_I2C1_SCL (7)
 #define MICROPY_HW_I2C1_SDA (6)
 #endif
+#endif
 
 // SDA/SCL on even/odd pins, I2C0/I2C1 on even/odd pairs of pins.
 #define IS_VALID_SCL(i2c, pin) (((pin) & 1) == 1 && (((pin) & 2) >> 1) == (i2c))